ok i will go step by step :
first create your stored procedure in sql server with the following :
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE PROCEDURE myInsertProcedure
@email nvarchar(50)
AS
BEGIN
SET NOCOUNT ON;
if not exists (select * from yourtable where email=@email )
begin
insert into yourtable(email) values(@email )
select 'inserted successfully'
end
else
begin
select 'the provided email already exists in our records'
end
END
GO
then go to your aspx page and create the markup below :
<asp: TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp: Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" />
lastly double click your button and type the following :
SqlConnection sqlCon = new SqlConnection("Data Source=ALPC28\\SERKANS2005;Initial Catalog=denemeler;Integrated Security=True;Pooling=False");
SqlCommand sqlCom = new SqlCommand();
sqlCom.CommandType = CommandType.StoredProcedure;
sqlCom.CommandText = "myInsertProcedure";
sqlCom.Connection = sqlCon;
SqlParameter sqlPar = new SqlParameter("@email", SqlDbType.VarChar);
sqlPar.Value = TextBox1.Text;
sqlCom.Parameters.Add(sqlPar);
string notification;
sqlCon.Open();
notification = sqlCom.ExecuteScalar().ToString();
sqlCon.Close();
Response.Write(notification);
i tried this creating a sample application, it works, just modify your connection string and adjust everything according to your webpage
Unsolved 
